Unknown,Transcriptomics,Genomics,Proteomics

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H3K27me3 ChIP-on-chip in T-ALL

ABSTRACT: Relative H3K27me3 enrichment, assessed by ChIP-on-chip, in two TLX positive and two TLX negative T Acute Lymphoblastique Leukemia (T-ALL) samples. Acute lymphoblastic leukemias (ALLs) are characterized by multi-step oncogenic processes leading to cell differentiation arrest and proliferation. Specific abrogation of maturation blockage constitutes a promising therapeutic option in cancer, which requires precise understanding of the underlying molecular mechanisms. We show that the cortical thymic maturation arrest in T-lineage ALL that over-express TLX1 or TLX3 is due to binding of TLX1/TLX3 to ETS1, leading to repression of the T cell receptor (TCR) alpha enhanceosome activity and blocked TCR-Jalpha rearrangement. TLX1/TLX3 abrogation or enforced TCRalpha/beta expression leads to TCRalpha rearrangement and apoptosis. Importantly, the auto-extinction of clones carrying TCRalpha-driven TLX1 expression supports TLX 'addiction' in TLX-positive leukemias and provides further rationale for targeted therapy based on disruption of TLX1/TLX3.

ORGANISM(S): Homo sapiens

SUBMITTER: Salvatore spicuglia

PROVIDER: E-MEXP-3527 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:A "Cartes d'Identite des Tumeurs" (CIT) project from the french Ligue Nationale Contre le Cancer (http://cit.ligue-cancer.net). 104 samples; Affymetrix U133A micro-arrays. Ninety two patients with T-ALL were diagnosed and treated at Saint-Louis hospital, Paris. Seven patients were studied at diagnosis and relapse (total 99 T-ALL samples). There were 56 children (median age 9 years old; range 1 to 16), and 36 adults (median age 27; range 17 to 66). Informed consent was obtained from the patients and/or relatives. T-ALL diagnosis was based on morphological and immunophenotypical criteria using flow cytometry and an extended monoclonal antibody panel. Using a combination of molecular cytogenetic and large-scale expression analysis in human T-ALL, we identified and characterized a new recurrent chromosomal translocation, targeting the major homeobox gene cluster HOXA and the TCRB locus. Specific quantitative PCR analysis showed that the expression of the whole HOXA gene cluster was dramatically dysregulated in the HOXA-rearranged cases, and also in MLL and CALM-AF10-related T-ALL cases, strongly suggesting that HOXA genes are oncogenic in these leukemias. Inclusion of HOXA-translocated cases in a general molecular portrait of 92 T-ALL based on large-scale expression analysis shows that this rearrangement defines a new homogeneous subgroup, which shares common biological networks with the TLX1 and TLX3-related cases. Since T-ALLs derive from T-cell progenitors, expression profiles of the distinct T-ALL subgroups were analyzed with respect to those of normal human thymic sub-populations. Inappropriate utilization or perturbation of specific molecular networks involved in thymic differentiation was detected. Moreover, we found a significant association between T-ALL oncogenic subgroups and ectopic expression of a limited set of genes, including several developmental genes, namely HOXA, TLX1, TLX3, NKX3-1, SIX6 and TFAP2C. These data strongly support the view that the abnormal expression of developmental genes, including the prototypical homeobox genes HOXA, is critical in T-ALL oncogenesis. Project Leader: FranC'ois Sigaux Institut Universitaire d'Hematologie Hopital Saint Louis, Paris, France Data submission: Fabien Petel

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H3K27me3 ChIP-on-chip in T-ALL

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